NASA and NOAA collaborate to test remote sensing technology for marine oil spill response

2023-12-25

Scientists from NASA and the National Oceanic and Atmospheric Administration (NOAA) are collaborating to test remote sensing technology for emergency response to marine oil spills.

On the Santa Barbara Coast of California, thousands of gallons of oil seep out of underwater cracks and rise to the surface every day. But thisnot a disaster zone. It is one of the largest natural oil spills in the world and is said to have been active for thousands of years.

The reliability of these leaks makes the region an important natural laboratory for scientists, including those involved in the Marine Oil Spill Thickness (MOST) project, a collaboration between NASA and NOAA to generate operable automatic oil spill detection, geospatial mapping analysis of oil extent, and oil thickness characterization applications.

The MOST team is working hard to develop a method for NOAA, the main federal agency for detecting and tracking coastal oil spills, to use remote sensing data not only to determine where the oil is, but also to determine where the thickest part is, which is one of the key components missing in direct response and remediation activities. The group recently concluded their autumn field trip in Santa Barbara.

"We are using a radar instrument called UAVSAR to describe the thickness of oil in the floating oil," said Cathleen Jones, a co researcher at the NASA Jet Propulsion Laboratory in Southern California. "This thicker oil stays in the environment for a longer period of time and causes greater damage to marine life than thin oil. If you know where it is, you can steer the reactor towards the problematic areas."

NASA's UAVSAR, also known as unmanned aerial vehicle synthetic aperture radar, is attached to the fuselage of an aircraft and collects images of an area approximately 12 miles wide (19 kilometers wide). But the synthetic aperture radar images are different from the images obtained by other sensors. The instrument sends radar pulses to the ocean surface, and the rebound signal is used to detect the roughness caused by waves on the ocean surface. When oil is present, it weakens the waves and creates a smoother water surface area. In synthetic aperture radar images, these smooth oily areas appear darker than the surrounding clean water - the thicker the oil, the darker the area appears.

Then, airborne observations must be validated, which means scientists must travel by boat to the same area and measure the thickness of oil by hand.

"We put the sampler, like a tube with both ends open, into water and let it stay there for a while," said Ben Holt, who is also a JPL co researcher at MOST. "Then when you close the pipe, a small layer of oil and water is collected. After the oil layer settles, you can measure the thickness of the oil layer and compare it with the observation results of UAVSAR to see their matching degree."

As another key verification layer, the ship deployed a drone carrying optical sensors that can observe floating oil and measure its thickness in a wider area than observed from the ship.

Initially, UAVSAR seemed unlikely to be a candidate device for tracking or describing oil. It is developed for measuring changes in the Earth's surface - for example, after earthquakes or volcanic eruptions. However, in the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, scientist Elijah Ramsey from the United States Geological Survey contacted Jones in an attempt to use the instrument to identify oil off the coast of Louisiana.

Jones said, "At the time, the signs indicated that this was impossible because the wavelength used by the instrument for this was too long. But we said, 'Anyway, we have to give it a try.'"

She and Holt are happy that they have done so. Jones said, "What you can see with UAVSAR is incredible because it is much more sensitive than satellite based instruments. Compared to typical satellite synthetic aperture radar instruments, UAVSAR is more sensitive to low echoes from oil covered areas. Therefore, we can identify petroleum and calculate the concentration of petroleum present."

Their discovery is a proof of concept and was published in 2012. In the following years, research was conducted on the feasibility of expanding this innovation for further risk analysis and evaluation.

In 2018, Frank Monaldo, a scientist from the University of Maryland who had been collaborating with NOAA for many years, collaborated with Jones, Holt, and teams from NOAA, the US Coast Guard, and the private sector, as well as researchers from Canada and Norway, to jointly develop the MOST proposal. In 2019, NASA's disaster project chose this concept for implementation to reduce disaster risk and enhance resilience, and the four-year MOST project was launched.

Unexpected, real-world deployment

When the MOST team was preparing to depart for autumn field activities, the plan was launched on the first Monday of October, and authorities were responding to reports of oil spills on the Huntington Beach coast of California - a location only 130 miles (209 kilometers) south of the Santa Barbara field activity site.

Several members of the MOST team quickly became involved in providing oil leakage data. Originally a controlled practice, it quickly became a real-world test of the effectiveness of UAVSAR in actual oil spill emergencies.

Jones said, "Thisreally different from practical activities because people are already overwhelmed when responding. But when NOAA received UAVSAR data, they used it to delineate oil, and then they released a marine pollution monitoring report based on it. Thisthe first time using data from airborne instruments to do this."

Although UAVSAR has been proven valuable in this situation, this deployment cannot replace field investigations for scientific purposes as they cannot be measured by ships. Holt said, "We really don't have in situ measurements for comparison. The real value is the efforts made by Cathleen and other members of the UAVSAR team to process and upload UAVSAR data, which can then be utilized by NOAA."

What is the next step?

Although UAVSAR's ability to detect oil spill thickness is useful, it is not practical to have aircraft fly over every area. Therefore, once the data from on-site activities in spring and autumn is validated, it will be used to train algorithms for automatically calculating oil thickness from SAR data.

UAVSAR is the prototype of an upcoming satellite mission called NASA-ISRO Synthetic Aperture Radar or NISAR, which is a collaborative project between NASA and the Indian Space Research Organization (ISRO). If everything goes according to plan, the methods and algorithms developed during the MOST project can also be applied to the data of new tasks.

Jones said, "The idea here is that in about two years, when the MOST project is completed, we will have a prototype system for detecting oil thickness that NOAA can use and distribute during oil spill response. Through NASA's collaboration with NOAA, we can transmit this information to those who can actually use it.".

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